Recently coronary artery spasm has become able to be induced experimentally. It has been reported that spasm was more easily induced when sclerotic changes pre-existed in the arterial walls. This study was attempted to study whether coronary spasm might accelerate a permeability in the coronary arteries, and proceed to further sclerotic changes.
The experimental group of dogs had been pretreated with denuding of endothelium of the left anterior descending arteries by a coil tip through coronary catheter with simultaneous ECG monitoring. Then, methacholine was injected intramuscularly, 1 time, 5 times, 10 times and 20 times, for 1 day to 27 days of total experimental period. The methacholine injection at the last time was under ECG monitoring, and when ECG showed ischemic changes such as ST elevation or depression, coronarycinearteriography was performed. Among 11 dogs, five showed spasm in non-denuded segments, usual further distal to denuded areas, of the coronary arteries. Evans blue was injected continuously into the pulmonary arteries for about 3 minutes. Ferritin also was injected at the same time, as a tracer for electron microscopical studies. After the coronary arteries were resected, they were cut through the long axis, and gross stain by Evans blue was observed on the intimal surface, then cut crossly at every 5mm width, each tissue block was numbered, and the odd numbers were made into microscopic sections. In every spastic segment, gross stain by Evans blue was observed and abnormal changes were found in intima and internal elastic layer, such as slight thickening of the intima and increased intimal cells, and fraying and widened fenestration of the inner elastic layer. Electron microscopical studies showed ferritin particles in inter-cellular spaces of intima and just beneath the internal lamela of media. Fat stain showed fine droplets besides the inner elastic layer.
These obtained results by the experiment may lead to a conclusion that repeated spasm makes abnormal changes of the intima and inner elastic layer, and vascular permeability increased. This fact suggests that spasm may be one of the risk factors of coronary sclerosis.
